Research And Application Of Functional Nanomaterials In Degradation Of Environmental Pollutants

With the rapid development of social economy,waste water pollution,especially dye wastewater pollution has become a serious environmental pollution problem in the world.Once the dye wastewater is discharged directly into the rivers and lakes,a large amount of organic compounds will consume dissolved oxygen in the water.At the same time,the dyestuffs with broad color will directly absorb the water light,reduce the transparency of the water,destroy the ecological balance of the water,posing a great threat to the health of humans and aquatic organisms.Based on this,the development of highly efficient technology for dye pollutant degradation based on functional nanomaterials,and its application in the treatment of industrial dye wastewater is of great significance.In recent years,chemical oxidative degradation method has attracted a great deal of attention,because it could efficiently convert the organic pollutants into harmless inorganic substances such as carbon dioxide and water,scientists have already made some progress.For instance,from the initial chemical oxidation to chemical oxidation with metal oxide and advanced oxidation processes?AOPs?using catalysts,from the traditional photocatalysis based on titanium dioxide to the novel photocatalytic degradation based on metal oxides and metal materials.Moreover,with the development of synthetic technology,new metal oxide nanomaterials and their composite materials are more controllable in size,morphology,composition,structure.All of these properties make the functional nanomaterials good candidate to realize dye degradation with high efficiency,and exhibit a broad propest in extending their application in the process of oxidative degradation,catalytic oxidative degradation and photocatalytic degradation.In this research,we focus on developing functional nanomaterials for dye wastewater treatment,including three parts:?1?In-situ generation of gold nanoparticles?Au-NPs?with ultra-small particle size on the surface of the manganese dioxide?MnO2?nanosheets.The obtained MnO2/Au-NPs nanocomposite had higher efficiency in oxidative degradation of methylene blue;?2?With redox activity infinite coordination polymer?ICP?as precursor,the CoO_x nanoparticles with ultra-small size were obtained by electrochemical polarization method.And then it could be attached to the surface of ITO glass stably with the doping of GO.The prepared CoO_x/GO nanocomposite supported on ITO glass could be used as efficient catalyst for oxidative degradation of methylene blue dye with hydrogen sulfide complex salt.With this kind of ITO glass as component,the reusable device could be built up for real-time monitoring the degradation of dye in industrial wastewater;?3?A novel bimetallic infinite coordination polymer particles?with cobalt and copper ions as the central ions/with cobalt and silver ions as the central ions?were developed and used as precursor for the CoO_x/CuO/Cu₂O or CoO_x/Ag/Ag₂O nanocomposite by electrochemical polarization.The visible-light catalytic activity of the as-formed nanocomposite was then evaluated by degradation of methylene blue in simulated visible light.The developed technology of dye wastewater treatment in this study not only paved a new avenue for the synthesis of functional metal oxides nanomaterials,but also was of great importance for the environmental water protection,the maintenance of human health and ecology environmental safety.This article was divided into four chapters as follows:Chapter 1.IntroductionIn this chapter,the pollution status and management of dye wastewater were analyzed and introduced.The existing methods for preparation of metal oxide nanomaterials and their applications in dye wastewater treatment were then summarized.The prospect of using the infinite coordination polymer particles as precursor for the synthesis of ultra-small size nanomaterials and its potential application in dye wastewater treatment were discussed.Finally,the main contents and significance of this paper were expounded.Chapter 2.Based on the nanocomposite of manganese dioxide and gold nanoparticles and its application in degradation of methylene blue dyesIn this chapter,the gold nanoparticles?Au-NPs?were in-situ generated on the surface of MnO2 nanosheets to form MnO2/Au-NPs nanocomposite in a simple and cost-effective way.Multiple experiments were carried out to optimize the MnO2/Au-NPs nanocomposite for the oxidative degradation of basic dye?methylene blue,MB?,including the molar ratio of MnO2 to HAuCl4,the pH of the solution and the effect of the concentration of initial material.Under the optimal condition,the highest degradation efficiency for MB achieved to 98.9%within 60 min,which was obviously better than commercial MnO2 powders?4.3%?and MnO2 nanosheets?74.2%?.The enhanced oxidative degradation might attribute to the in-situ generation of ultra-small and highly-dispersed Au-NPs which enlarged the synergistic effect and/or interfacial effect between MnO2 nanosheets and Au-NPs and facilitated the uptake of electrons by MnO2 from MB during the oxidation,the results showed that the application of MnO2/Au-NPs nanocomposite for removal of organic dyes from wastewater in a simple and convenient fashion.Chapter 3.Based on the nanocomposite of CoO_x/GO nanocomposite prepared by electrochemical polarization of ICP and its application in the degradation of organic dyesIn this chapter,we for the first time developed an efficient and portable UV detection pool for catalytic degradation of dye in industial wastewater.Initially,redox-active infinite coordination polymer {Co?3,5-dbsq??3,5-dbcat??bix?} ICP was drop-coated on ITO glass.By electrochemical polarizing ICP supported on the surface of ITO glass,highly-dispersed CoO_x NPs with ultra-small size and narrow size disturibution were in-situ generated on ITO glass.Graphene oxide?GO?were next mixed with ICP to obtain ITO supported CoO_x/GO nanocatalyst with higher electron transport rate and enhanced stability.The catalytic activity of this ultra-small CoO_x/GO nanocatalyst were then optimzied by looking at the degradation efficiency of methylene blue?MB?via oxidative degradation process in presence of oxone.Under the optimal conditon here,100%MB could be decomposed within 100s,which is found better than other CoO_x nanocatalysts.With this kind of ITO glass as elements,a portable UV detection pool was constucted for real-time monitoring the catalytic degradation of dye in wastewater from textile and costmetic industy directly.This study not only offered a novel water purification technology for dye wastewater treatment with simplicity,but also provided a universal strategy for the preparation of highly efficient nanocatalysts with infinite coordination polymer as precursor.Chapter 4.Based on the nanocomposite of CoO_x/CuO/Cu₂O and CoO_x/Ag/Ag₂O prepared by electrochemical polarization of ICP and its application in degradation of organic dyesIn this chapter,the CoO_x/CuO/Cu₂O nanocomposite and CoO_x/Ag/Ag₂O nanocomposite were obtained by two-steps polarization and one-step polarization of bimetallic ICP?Co and Cu as the metal ions/Co and Ag as the metal ions?as precursor,respectively.In order to realize higly effient photocatalytic degradation of methylene blue,the molar ratio of cobalt ion to copper ion,the amount of the initial material were optimized.Under the optimal conditions,the degradation efficiency of methylene blue with the presence of CoO_x/CuO/Cu₂O nanocomposite could reach 100%at 420 min,which was better than that of CoO_x/Ag/Ag₂O nanocomposite?79%?,pure CoO_x nanomaterial?63%?and only light?12%?.Moreover,since the nanocomposites were attached to the surface of the ITO glass,so it could be used repeatedly in a convenient manner.The degradation efficiency of this material could still achieve 59.8%compared with the initial one?better than that of CoO_x/Ag/Ag₂O nanocomposite?28.7%??when it had been reused for six times.Results demonstrated that the as-prepared CoO_x/CuO/Cu₂O nanocomposite exhibited good photocatalytic degradation ability,which allowed for the removal of organic pollutants from wastewater easily by clean and green energy.